中国稻田土壤有机质时空变化及其驱动因素

【目的】评价中国稻田土壤有机质时空变化特征,为提高耕地质量,应对种植结构调整及气候变化等提供支撑。【方法】基于1988—2017年开展的338个国家级定位监测点,分析稻田耕层土壤有机质含量变化特征、驱动因素以及对土壤容重影响。【结果】近30年全国稻田耕层土壤有机质平均提高了3.49 g·kg^-1,年均增速0.09—0.12 g·kg^-1。稻田耕层土壤有机质含量年均增速高低依次为东北、长江下游、长江中游、华南和西南。目前,全国稻田耕层土壤有机质平均含量32.4 g·kg^-1,从高到低依次为长江中游、华南、东北、西南和长江下游。气候、土壤类型、氮肥投入以及种植制度等对土壤有机质产生影响。西南稻区和高纬度的东北稻区,稻田土壤有机质含量与年均气温显著负相关（P<0.05）,东部地区和低纬度的地区稻田土壤有机质含量与年均气温显著正相关（P<0.05）。潜育型水稻土有机质平均含量显著高于其他类型水稻土。合适的氮肥投入量（200—300 kgN·hm^-2·a^-1）有利于土壤有机质累积。土壤容重及耕层深度与土壤有机质存在显著响应关系（P<0.01）。【结论】我国稻田耕层土壤有机质含量整体呈上升趋势,年均增速呈现从南到北依次增加的趋势。年均气温和降水量,土壤类型,氮肥用量和种植制度等管理措施是区域土壤有机质含量分异的主要驱动因子。

Spatio-Temporal Variations of Soil Organic Matter in Paddy Soil and Its Driving Factors in China

【Objective】 Spatio-temporal variation characteristics of soil organic matter (SOM) in paddy fields were evaluated in China, which would provide support for the improving the quality of cultivated land, adjustment of planting structure and climate change. 【Method】 The characteristics of SOM change and its driving factors were analyzed based on 338 national long-term monitoring sites, which were carried out in different rice planting regions from 1988 to 2017. The effects of SOM on soil bulk density were also studied. 【Result】 The SOM content of the paddy field in China increased by 3.49 g·kg^-1 in averaged in the past 30 years, which was increased at the rate of 0.09-0.12 g·kg^-1 annually. The average increased rate of SOM content ranked from high to low were Middle of Yangtze River region (MYR), South of China (SC), Northeast of China (NE), Southwest of China (SW) and Lower of Yangtze River (LYR). The average SOM content of the paddy field was 32.4 g·kg^-1 in China at present, which was highest in MYR, followed by SC, NE, SW and LYR. The SOM content were responded by climate, soil types, nitrogen (N) fertilizer input, and cropping system. There was a significantly negative correlation relationship between SOM content and annual mean temperature in SW region and high latitude regions (P<0.05), and it was a positive correlation relationship in East region and low latitudes region (P<0.05). The average SOM content in gleyic paddy soil was significantly higher than that in other types of paddy soil. N fertilizer input at 200-300 kg N·hm^-2·a^-1 was conducive to SOM accumulation. There was strong response between soil bulk density and SOM, plough layer depth and SOM significantly (P<0.01). 【Conclusion】 The SOM content of the paddy field in China showed an upward trend in the past 30 years. The average increased rate of SOM content annually showed an increasing trend from South to North of China. The average annual temperature, annual precipitation, paddy soil types and nitrogen fertilizer application were the main driving factors to the SOM content of paddy field in China.